180 ALASKAN MINERAL RESOURCES IN 1906. 
It is equally well known that as yet, with the exception of a few claim 
no gravels of very high grade have been developed. Certain cone 
tions already referred to are favorable to the probable extension of tl 
placer-mining industry. One of these is the wide extent of the miner 
alization. If, as stated elsewhere in this report (pp. 25, 130-132! 
the zones of mineralization of the peninsula are most commonly foul 
along or near the contacts of mica schist and limestone, the Kougaro 
is a region where placers should be expected. As in other minera 
bearing districts of the peninsula, the bed rock is closely foldec 
faulted, and fractured, and mineralized quartz stringers are no 
uncommon, but have not been tested as to their gold content. I 
at least two localities the gold has been traced to its bed-rock sourc 
in the schists. So far as the present studies can determine, the be 
rock is no less favorable for the occurrence of gold here than in othe 
districts of the peninsula. 
The history of this province since it was last elevated above th 
sea, interpreted according to theories elsewhere presented, favors tl 
concentration of gold in the alluvial deposits. The various epochs < 
erosion indicated by the bench deposits would promote the concen 
tration of the heavier materials in the gravels. In several localities 
on Kougarok River the gold was probably derived by reconcentratioi 
from older elevated placers. Yet it must be said that, in spite of th 
reconcentration, the resulting placers have not been found to be a 
rich as those of similar origin in other parts of the peninsula. Th 
fact points toward the conclusion that the bed-rock source is not a 
heavily mineralized as in some of the other districts. The lower bene 
gravels of the Kougarok and some of its tributaries are undoubtedly 
among the most important deposits of the district, if only because o 
their favorable position for cheap mining. The highest gravels (i. e. 
those above 50 or 60 feet) reported at various places have now littL 
prospect of development unless they are far richer than any of th 
other deposits. Their topographic position makes it difficult, if no 
impossible, to hydraulic except at great cost. Experience has show] 
that the abundance of the ground ice, the limestone masses, an< 
heavy talus all combine to make ditch construction and maintenanc 
expensive. 
The writer is unable to make a definite statement of the gold teno 
of the gravels in this field, for the results of the little prospecting tha 
has been done have not been available for the purposes of this report 
When the meager evidence is carefully weighed, it seems probable thai 
$2 to the cubic yard must be considered high value for most of th 
placers of the district. Whether or not there are considerable bodie 
of gravel which carry such values, the writer is not prepared to state i 
While a gold tenor of $2 would be considered very rich in most place 
camps, it is low compared with that of some of the auriferous gravel 
